Bulk silicon mirrors with hinges underneath

ABSTRACT

This invention provides method and apparatus for fabricating a MEMS apparatus having a bulk element with hinges underneath. The bulk element may comprise single-crystal silicon, fabricated by way of bulk micromachining techniques. The hinges may be made of thin-films, fabricated by way of surface micromachining techniques. A distinct feature of the MEMS apparatus of the present invention is that by disposing the hinges underneath the bulk element, the surface of the bulk element can be maximized and the entire surface becomes usable (e.g., for optical beam manipulation). Such a feature would be highly advantageous in making arrayed MEMS devices, such as an array of MEMS mirrors with a high optical fill factor. Further, by advantageously making use of both bulk and surface micromachining techniques, a MEMS mirror thus produced is equipped with a large and flat mirror along with flexible hinges, hence capable of achieving a substantial rotational range at modest electrostatic drive voltages.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of U.S. Provisional PatentApplication No. 60/295,682, filed on 2 Jun. 2001, which is incorporatedherein by reference for all purposes.

FIELD OF THE INVENTION

[0002] This invention relates generally to micro-electro-mechanicalsystems (MEMS). In particular, it provides method and system for makingMEMS mirrors by a combination of bulk and surface micromachiningtechniques.

BACKGROUND OF THE INVENTION

[0003] MEMS mirrors have demonstrated to be effective in a variety ofapplications, including high-speed scanning and optical switching. Insuch applications, it is essential for MEMS mirrors to have flat opticalsurfaces, large rotational range, and robust performance.

[0004] Many applications (e.g., optical networking applications) furtherrequire that MEMS mirrors be configured in a closely packed array. It istherefore desirable to maximize the “optical fill factor” of the array(i.e., by making the optical surface of each constituent mirror as largeas possible), without compromising other essential characteristics.

[0005] MEMS mirrors are conventionally made by either bulk or surfacesilicon micromachining techniques. Bulk micromachining, which typicallyproduces single-crystal silicon mirrors, is known to have a number ofadvantages over surface micromachining, which typically producespolysilicon (or thin-film) mirrors. For example, single-crystal siliconmirrors produced by bulk micromachining techniques are generally thickerand larger mirrors with smoother surfaces and less intrinsic stress thanpolysilicon (or thin-film) mirrors. Low intrinsic stress and sizeablethickness result in flat mirrors, while smooth surfaces reduce lightscattering. An advantage inherent to surface micromachining techniquesis that the mirror suspension (e.g., one or more thin-film hinges) canbe better defined and therefore made smaller. This allows the MEMSmirror thus produced to have a large rotational range, e.g., at moderatedrive voltages.

[0006] U.S. Pat. No. 6,028,689 of Michalicek et al. (“Michalicek etal.”) discloses a movable micromirror assembly, driven by anelectrostatic mechanism. The assembly includes a mirror supported by aplurality of flexure arms situated under the mirror. The flexure armsare in turn mounted on a support post. Because the assembly disclosed byMichalicek et al. is fabricated entirely by way of surfacemicromachining techniques, the resulting “micromirror” is of thepolysilicon (thin-film) type and is thus subject to the aforementioneddisadvantages.

[0007] International Patent Application Number WO 01/94253 A2 of Chonget al. discloses a MEMS mirror device having a bulk silicon mirrorattached to a frame by thin-film hinges. A notable shortcoming of thissystem is evident in that the thin-film hinges extend from thereflective surface side of the mirror to the frame, hence restricting(or obstructing) the amount of surface area available for optical beammanipulation. This shortcoming further results in a lower optical fillfactor in an array of such MEMS devices.

[0008] Tuantranont et al. disclose an array of deflectable mirrorsfabricated by a surface micromachining polysilicon (or “MUMPS”) processin “Bulk-Etched Micromachined and Flip-Chip Integrated Micromirror Arrayfor Infrared Applications,” 2000 IEEE/LEOS International Conference onOptical MEMS, 21024, Kauai, Hi. (August 2000). In this case, an array ofpolysilicon mirror plates is bonded to another array of thermal bimorphactuators by gold posts using the “flip-chip transfer technique”,resulting in trampoline-type polysilicon plates each suspended at itscorners by thermal bimorph actuators. In addition to the mirror platesmade of polysilicon (or thin-film), another drawback of thethus-constructed mirror array is the lack of a monolithic structure,which makes the array susceptible to misalignment and other extraneousundesirable effects.

[0009] In view of the foregoing, there is a need in the art to provide anovel type of MEMS mirrors that overcomes the limitations of priordevices in a simple and robust construction.

SUMMARY OF THE INVENTION

[0010] The present invention provides a MEMS apparatus, including a bulkelement; a support; and one or more hinges. The bulk element comprises adevice surface and a bottom surface that is situated below the devicesurface. The hinges are disposed below the bottom surface of the bulkelement and couple the bulk element to the support, whereby the bulkelement is suspended from the support.

[0011] In the above apparatus, the support may include a cavity, inwhich the hinges are disposed. There may be at least one electrodedisposed in the cavity, for causing the bulk element to be actuated. Thedevice surface of the bulk element may further contain a reflectivelayer (e.g., a metallic film), rendering the apparatus thus constructeda MEMS mirror.

[0012] In the present invention, the term “bulk element” refers to anelement fabricated by bulk micromachining techniques known in the art,which typically comprises a single-crystal material. A case in point maybe a single-crystal silicon element. The bulk element is characterizedby a “device” surface and a “bottom” surface that is situated below thedevice surface (while the bulk element itself may assume any geometricform deemed suitable). The “device” surface of the bulk element may beoptically reflective. It may also be used as an “interface” for couplingthe bulk element to other devices, if so desired in a practicalapplication. Further, a “support” may be a frame or substrate, to whichthe bulk element is attached. A “hinge” (or “hinge element”) should beconstrued broadly as any suspension/coupling means that enables the bulkelement to be suspended from the support and further provides therestoring force as the bulk element undergoes motion. For instance, ahinge may be a flexure or flexible coupling, e.g., fabricated by a bulkor surface micromachining technique known in the art. The term“underneath” refers to the hinges being anchored to (or below) thebottom surface of the bulk element and thereby disposed wholly beneaththe device surface. This allows the device surface of the bulk elementto be maximized and the entire surface to be usable (e.g., for opticalreflection).

[0013] The present invention further provides a process flow (or method)that may be used for fabricating the aforementioned MEMS apparatus. Inone embodiment of a process flow according to the present invention, a“device” component is formed. The device component in one form may beprovided by an SOI (Silicon-On-Insulation) wafer, comprising asingle-crystal silicon device layer and a silicon handle wafer with aninsulation layer (e.g., silicon oxide) sandwiched in between. First andsecond hinge elements may be fabricated on a first surface of thesingle-crystal silicon layer, e.g., by way of surface micromachiningtechniques. A “support” component is configured to contain a cavity, inwhich at least one electrode may be disposed. Subsequently, the deviceand support components are bonded in such a manner that the hingeelements are disposed within the cavity. The silicon handle wafer alongwith the insulation layer in the device component is then removed,thereby revealing a second surface of the single-crystal silicon devicelayer. A bulk element may be subsequently produced in the single-crystalsilicon device layer by way of bulk micromachining techniques,characterized by the first and second surfaces. The configuration may besuch that the hinge elements are each anchored to the first (or“bottom”) surface of the bulk element on one end and to the supportcomponent on the other, thereby enabling the bulk element to besuspended with the hinge elements wholly underneath the second (or“device”) surface. A reflective layer may be further deposited on thedevice surface of the bulk element, rendering the apparatus thusconstructed a MEMS mirror.

[0014] One advantage of the MEMS apparatus of the present invention isthat by placing the hinge elements underneath the bulk element, thedevice surface of the bulk element can be maximized and the entiresurface becomes usable (e.g., for optical beam manipulation). Such afeature would be highly advantageous in making arrayed MEMS devices,such as an array of MEMS mirrors with a high optical fill factor.Further, by advantageously making use of both bulk and surfacemicromachining techniques, a MEMS mirror of the present invention isequipped with a large and flat mirror along with flexible hinges, and ishence capable of achieving a substantial rotational range at moderateelectrostatic drive voltages. An additional advantage of the MEMSapparatus of the present invention is evident in its monolithicstructure, rendering it robust in performance. These advantageousfeatures are in notable contrast with the prior devices described above.

[0015] The novel features of this invention, as well as the inventionitself, will be best understood from the following drawings and detaileddescription.

BRIEF DESCRIPTION OF THE FIGURES

[0016]FIG. 1A is a schematic side sectional view of a first embodimentof a MEMS apparatus, according to the present invention;

[0017]FIG. 1B is a schematic top view of a first embodiment of a MEMSapparatus, according to the present invention;

[0018]FIG. 2 is a schematic side sectional view of a second embodimentof a MEMS apparatus, according to the present invention;

[0019]FIG. 3 is a schematic side sectional view of a third embodiment ofa MEMS apparatus, according to the present invention; and

[0020] FIGS. 4A-4F show an exemplary process flow for fabricating a MEMSapparatus, according to the present invention.

DETAILED DESCRIPTION

[0021] FIGS. 1A-1B illustrate a first embodiment of a MEMS apparatus,according to the present invention. FIG. 1A depicts a schematic sidesectional view of a MEMS apparatus 100, comprising a bulk element 110;first and second hinge elements 121, 122; and a support 130. The bulkelement 110 may have a “device” (or “top”) surface 112, and a “bottom”surface 111 which is disposed below and opposes the device surface 112.The first and second hinge elements 121, 122 are each disposed below thedevice surface 112. As a way of example in the embodiment of FIG. 1A,the hinge elements 121, 122 are each coupled to the bottom surface 111of the bulk element 110 on one end and to the support 130 on the other.In this manner, the bulk element 110 is suspended with the hingeelements 121, 122 disposed wholly underneath the device surface 112.

[0022]FIG. 1B shows a schematic top view of the MEMS apparatus 100. Byway of example, the device surface 112 of the bulk element 110 is shownto be generally rectangular in shape. It will be appreciated that thisneed not be case; in fact, the device surface of a bulk element (or thebulk element itself) in the present invention may assume any geometricform (e.g., elliptical) that is deemed suitable for a given application.

[0023] In the embodiment of FIGS. 1A-1B, the support 130 may include asubstrate portion 131 and a cavity 140. By way of example, the substrateportion 131 may be generally rectangular in shape. A plurality ofsidewalls 132, 133, 134, 135 may extend from the portion 131 and therebyform the cavity 140. As shown in FIG. 1A, the hinge elements 121, 122are disposed within the cavity 140, and are coupled respectively to thesidewalls 133, 135. In the embodiment of FIGS. 1A-1B, each of thesidewalls 132, 133, 134, 135 may include a corresponding ridge (or“lip”) portion 142, 143, 144, 145 that projects inward from therespective sidewall (see the ridge portions 143, 145 shown in FIG. 1A,for example). Furthermore, the hinge elements 121, 122 have a generally“C”-shaped (side-view) cross-section, and are coupled to the ridgeportions 143, 145 of the sidewalls 133, 135, respectively. However, thisshould not be viewed as limiting in any way. For example, in alternateembodiments, the hinge elements 121, 122 may assume any other suitableshape or cross-section. They may also be coupled to other portions ofthe sidewalls 133, 135.

[0024] In the embodiment shown in FIGS. 1A-1B, the cavity 140 is shownto be generally rectangular in shape. However, in alternate embodiments,the cavity 140 may assume any other suitable geometric form. The cavity140 may include at least one electrode 141, which may be disposed on abottom surface 150 of the cavity 140. The electrode 141 is adapted tocause the bulk element 110 to be actuated in a known manner (e.g., in anelectro-static fashion). Moreover, the device surface 112 of the bulkelement 110 may be optically reflective, e.g., by way of polishingand/or depositing a metallic film on the surface.

[0025]FIG. 2 shows a schematic side sectional view of a secondembodiment of a MEMS apparatus. By way of example, MEMS apparatus 200may comprise a bulk element 210; first and second hinge elements 221,222; and a support 230. The bulk element 210 may include a “device” (or“top”) surface 212, and a “bottom” surface 211 which is disposed belowand opposes the device surface 212. In this embodiment, the bulk element210 may further include a base portion 215, which may extend downwardfrom the bottom surface 211. The first and second hinge elements 221,222 are each disposed below the device surface 212. As a way of example,the first and second hinge elements 221, 222 are each shown to becoupled to the base portion 215 of the bulk element 110 on one end andto the support 130 on the other. In this manner, the bulk element 210 issuspended with the hinge elements 221, 222 disposed wholly underneaththe device surface 212.

[0026] In the embodiment of FIG. 2, the support 230 may include asubstrate portion 231 and a cavity 240. By way of example, the substrateportion 231 may be generally rectangular in shape. A plurality ofsidewalls 233, 235 extend from the portion 231 and thereby form thecavity 240. The hinge elements 221, 222 are disposed within the cavity240. In the present embodiment, the hinge elements 221, 222 may extendin a generally horizontal direction, thereby coupling the base portion215 to the sidewalls 233, 235, respectively. However, this should not beviewed as limiting in any way. For example, in alternate embodiments,the hinge elements 221, 222 may assume any other suitable shape. Theymay also be positioned in other directions, and/or coupled to otherportions of the sidewalls 233, 235.

[0027] The cavity 240 may be of any suitable shape in the embodiment ofFIG. 2. The cavity 240 may include at least one electrode 241, which maybe disposed on a bottom surface 250 of the cavity 240. The electrode 241is adapted to cause the bulk element 210 to be actuated in a knownmanner (e.g., electro-statically). The device surface 212 of the bulkelement 210 may likewise be optically reflective, e.g., by way ofpolishing and/or depositing a metallic film on the surface.

[0028]FIG. 3 shows a schematic side sectional view of a third embodimentof a MEMS apparatus 300. With the exception of a bulk element 310, MEMSapparatus 300 is shown to be substantially similar to the MEMS apparatus200, and may make use of the general configuration of and a number ofthe elements shown in FIG. 2. As shown in FIG. 3, the MEMS apparatus 300may comprise a bulk element 310; first and second hinge elements 321,322; and a support 330. The support 330 may include a cavity 340, whichis formed by at least two sidewalls 333, 335 that extend from substrateportion 331. The cavity 340 may include a bottom surface 350, on whichat least one electrode 341 may be disposed.

[0029] In the MEMS apparatus 300, the bulk element 310 may include a“device” (or “top”) surface 312, and a “bottom” surface 311 which isdisposed below and opposes the device surface 312. As a way of example,the bulk element 310 is shown to include a generally “T”-shaped baseportion 315. The base portion 315 extends downward from the bottomsurface 311 and forms side cavities or “voids” 316, 317 in the bulkelement 310. As in the embodiment of FIG. 2, the first and second hingeelements 321, 322 are each disposed beneath the bottom surface 311 ofthe bulk element 310. In the present embodiment, the hinge elements 321,322 are each shown to be coupled to the base portion 315 of the bulkelement 310 within the respective voids 316, 317 on one end and to therespective sidewalls 333, 335 of the support 330 on the other. In thismanner, the bulk element 310 is suspended with the hinge elements 321,322 disposed wholly underneath the device surface 312.

[0030] In the foregoing embodiments and in an exemplary fabricationprocess described below, the term “bulk element” (e.g., the bulk element110, 210, or 310) refers to an element fabricated by bulk micromachiningtechniques known in the art, which typically comprises a single-crystalmaterial. For example, the bulk elements 110, 210, 310 shown above mayeach be a single-crystal silicon element. The bulk element ischaracterized by a “device” surface and a “bottom” surface that issituated below the device surface; while the bulk element itself mayassume any geometric form that is appropriate for a given application.(It will be appreciated that the device and bottom surfaces need not beopposing one another, in general.) The “device” surface of a bulkelement may be optically reflective. An optical element (e.g., agrating) may also be patterned on it. Additionally, the device surfacemay be used as an “interface” for coupling the bulk element to otherdevices, if so desired in practical applications.

[0031] Further, a “support” (e.g., the support 130, 230, or 330) may bea frame or substrate, to which the bulk element is attached. A “hinge”(or “hinge element”) should be construed broadly as anysuspension/coupling means that enables the bulk element to be suspendedfrom the support and further provides the restoring force as the bulkelement undergoes motion (e.g., due to the actuation mechanism caused bythe electrode 141 of FIGS. 1A-1B). As a way of example, the first orsecond hinge element shown in FIG. 1A, 2, or 3 may be a flexure orflexible coupling, e.g., fabricated by bulk or surface micromachiningtechniques known in the art. While two hinge elements are shown in eachof the foregoing embodiments, alternate embodiments may include a feweror greater number of hinge elements. The term “underneath” refers to ahinge element being anchored to (or below) the bottom surface of thebulk element and thereby disposed wholly beneath the device surface.This allows the device surface of the bulk element to be maximized andthe entire surface to be usable (e.g., for optical beam manipulation),as the above embodiments illustrate.

[0032] FIGS. 4A-4F show an exemplary embodiment of a process flow, whichmay be utilized for fabricating a MEMS apparatus (e.g., the embodimentof FIGS. 1A-1B) according to the present invention. FIG. 4A shows aschematic side sectional view of a “device” component 400, which in oneform may be an SOI (Silicon On Insulator) wafer, comprising asingle-crystal silicon “device” layer 415 and a silicon “handle wafer”417 with a first insulation layer 416 (e.g., silicon oxide) sandwichedtherein between. The single-crystal silicon device layer 415 may have apredetermined thickness d, which may be on the order of 5-100 μm. Firstand second hinge elements 421, 422 are fabricated on a first surface 411of the single-crystal silicon device layer 415 in a known manner, e.g.,by a known surface micromachining technique. Each hinge element may be athin-film, e.g., composed of polysilicon, polyoxide, nitride, siliconnitride, silicon oxide, silicon oxynitride, or a metal. First and second“sacrificial” elements 423, 424 (which may be formed from silicon oxide)may be first patterned on the first surface 411, prior to forming thefirst and second hinge elements 421, 422, respectively.

[0033]FIG. 4B shows a schematic side sectional view of a “support”component 450 containing an “open-ended” cavity 440. As a way ofexample, the cavity 440 may be formed by a substrate wafer 431 and aplurality of spacers 433, 435 which form sidewalls of the cavity 440.There may be at least one electrode 441 disposed in the cavity 440,e.g., patterned on the substrate wafer 431 via a second insulation layer432 which may be made of silicon oxide.

[0034] Referring now to FIG. 4C. The device component 400 formed in FIG.4A is bonded with the support component 450 of FIG. 4B in such a mannerthat the first and second hinge elements 421, 422 are disposed (oraccommodated) within the cavity 440. In the next step of the fabricationprocess flow, illustrated in FIG. 4D, the silicon handle wafer 417(along with the first insulation layer 416) is removed, therebyrevealing a second surface 412 of the single-crystal silicon devicelayer 415.

[0035] In the subsequent step of the fabrication process flow, depictedin FIG. 4E, a “bulk element” 410 is formed in the single-crystal silicondevice layer 415 by a known bulk micromachining technique (e.g., a DRIE(Deep Reactive Ion Etching) process) known in the art. The formed bulkelement 410 is also characterized by the first and second surfaces 411,412 that oppose one another. In the next step of the fabrication processflow, shown in FIG. 4F, the bulk element 410 is “released”, e.g., byremoving the first and second sacrificial elements 423, 424. Note thatthe remainder of the single-crystal silicon device layer 415, thespacers 433, 435, and the support wafer 431 form an integrated supportstructure 430, which may substantially constitute the support 130 in theembodiment of FIGS. 1A-1B, for instance. (Those skilled in the art willappreciate that first and second sacrificial elements 423, 424 may alsobe removed earlier, e.g., anywhere in the fabrication process flow afterthe step of FIG. 4A.)

[0036] A reflective layer 402 (e.g., a gold film) may be furtherdeposited on the second surface 412 of the bulk element 410, renderingthe apparatus thus constructed a MEMS mirror. Note that because thefirst and second hinge elements 421, 422 are anchored to the first (or“bottom”) surface 411 and thereby wholly “underneath” the bulk element410 thus produced, the second (or “device”) surface 412 of the bulkelement 410 can be maximized and the entire surface becomes usable(e.g., for optical reflection). Furthermore, being situated in a cavity(e.g., the cavity 440), the first and second hinge elements 421, 422 canbe made sufficiently long/large, if so desired in a given application.

[0037] In the aforementioned process flow, use of an SOI wafer for thedevice component 400 of FIG. 4A has the advantages of providing precisecontrol of the thickness of the bulk element 410 (by way of thepredetermined thickness d of the single-crystal silicon device layer ofthe SOI wafer) and ease in manipulation (owing to the handle wafer ofthe SOI wafer), while the intervening insulation layer of the SOI wafermay serve as a convenient “etch-stop” (e.g., when removing the handlewafer). The hinge elements may also be fabricated by a known bulkmicromachining technique (e.g., the SCREAM (Single Crystal ReactiveEtching and Metallization) process known in the art). It will beappreciated, however, that a device component in the present inventionmay alternatively be formed in an epitaxial silicon wafer, or a singlepiece of single-crystal silicon, where the hinge elements may befabricated in a manner similar to that described above.

[0038] The support component 450 of FIG. 4B may likewise be fabricatedout of an SOI wafer which may be similar to that shown in FIG. 4A inconfiguration. As a way of example, the silicon device layer (e.g.,50-100 μm in thickness) of the SOI wafer may be used to form the spacers433, 435 along with the electrode 441 (e.g., by way of etching), whilethe corresponding handle wafer may serve as the substrate wafer 431.Alternatively, a glass wafer may be used to form the substrate wafer431, on which the electrode 441 may be deposited (e.g., by a knownsurface micromachining technique) and the spacers 433, 435 (e.g., madeof silicon) bonded. The support component 450 of FIG. 4B may also befabricated out of a single piece of a desired material (e.g., a siliconor glass wafer) using an appropriate technique known in the art. Thoseskilled in the art will appreciate that a support component in thepresent invention may generally be configured in any way that issuitable for a given application; what is important is that the supportelement thus configured contains an open-ended cavity (so as to host thehinge elements), e.g., in a manner as illustrated with respect to FIG.4B.

[0039] A distinct feature of the fabrication process flow of FIGS. 4A-4Fis that the device component 400 and the support component 450 arebonded in such a manner that the hinge elements are disposed within (oraccommodated by) the cavity 440 of the support component 450 (e.g., seeFIG. 4C above), thereby allowing the hinge elements to be situated“underneath” the bulk element thus produced. One skilled in the art willknow how to apply a suitable process known in the art that is effectivefor carrying out the requisite bonding (e.g., fusion or anodic bonding).It will be appreciated that various elements in the embodiment of FIGS.4A-4F are shown as a way of example to illustrate the general principlesof the present invention, and therefore are not drawn to scale (e.g., ineither geometric shape or size). From the teaching of the presentinvention, those skilled in the art will know how to implement thefabrication process flow of FIGS. 4A-4F in a given application, toproduce a suitable MEMS apparatus according to the present invention.

[0040] An advantage of the MEMS apparatus of the present invention isthat by placing the hinge elements underneath the bulk element, thedevice surface of the bulk element can be maximized and the entiresurface becomes usable (e.g., for optical beam manipulation). Such afeature would be highly advantageous in making arrayed MEMS devices,such as an array of MEMS mirrors with a high optical fill factor.Further, by advantageously making use of a combination of bulk andsurface micromachining techniques, a MEMS mirror according to thepresent invention may be equipped with a large and flat mirror alongwith flexible hinges, thereby capable of providing a substantialrotational range at moderate electrostatic drive voltages. An additionaladvantage of the MEMS apparatus of the present invention is evident inits monolithic structure, rendering it robust in performance. Theseadvantageous features are in notable contrast with the prior devicesdescribed above. As such, the present invention may be used in a varietyof applications, e.g., providing arrayed MEMS mirrors (or beam steeringdevices) for optical networking applications.

[0041] Those skilled in the art will recognize that the exemplaryembodiments described above are provided by way of example to illustratethe general principles of the present invention. Various means andmethods can be devised herein to perform the designated functions in anequivalent manner. Moreover, various changes, substitutions, andalternations can be made herein without departing from the principlesand the scope of the invention. Accordingly, the scope of the presentinvention should be determined by the following claims and their legalequivalents.

What is claimed is:
 1. An apparatus comprising: a) a bulk element havinga device surface and a bottom surface, disposed below said devicesurface; b) a support; and c) at least one hinge, which is disposedbelow said bottom surface, and which is coupled to said bulk element andto said support, thereby suspending said bulk element from said support.2. The apparatus of claim 1 wherein said bulk element comprisessingle-crystal silicon.
 3. The apparatus of claim 1 wherein said devicesurface is reflective.
 4. The apparatus of claim 3 wherein said devicesurface comprises a reflective layer.
 5. The apparatus of claim 4wherein said reflective layer comprises a material selected from thegroup consisting of gold, aluminum, silver, and copper.
 6. The apparatusof claim 1 wherein said at least one hinge is formed from a materialselected from the group consisting of polysilicon, polyoxide, nitride,silicon nitride, silicon dioxide, silicon oxynitride, single-crystalsilicon, and metals.
 7. The apparatus of claim 1 wherein said support ismade of silicon.
 8. The apparatus of claim 1 wherein said supportincludes a cavity, and wherein said at least one hinge is disposedwithin said cavity.
 9. The apparatus of claim 8 wherein said supportfurther comprises at least one electrode disposed in said cavity, forcausing said bulk element to be actuated.
 10. The apparatus of claim 8wherein said cavity is formed by a plurality of sidewalls.
 11. Theapparatus of claim 10 wherein said at least one hinge comprises firstand second hinge elements, and wherein each of said hinge elements iscoupled to a unique one of said plurality of sidewalls.
 12. Theapparatus of claim 11 wherein each of said sidewalls includes a ridgeportion that is inwardly projecting, and wherein each of said hingeelements is coupled to a unique one of said ridge portions.
 13. Theapparatus of claim 12 wherein each of said hinge elements is furthercoupled to said bottom surface.
 14. The apparatus of claim 11 whereinsaid bulk element further comprises a base portion which extendsdownward from said bottom surface, and wherein each of said hingeelements is coupled to said base portion.
 15. A method of making a MEMSapparatus, comprising: a) providing a device component comprisingsingle-crystal silicon; b) creating at least one hinge in said devicecomponent; c) constructing a support component having a cavity; d)bonding said device component to said support component, such that saidat least one hinge is disposed within said cavity; and e) forming insaid device component a bulk element having a device surface and abottom surface, whereby said at least one hinge is coupled to said bulkelement and is disposed below said bottom surface, thereby suspendingsaid bulk element from said support.
 16. The method of claim 15 whereinsaid device component comprises an SOI (Silicon-On-Insulator) waferhaving a single-crystal silicon device layer and a silicon handle wafersandwiching an insulation layer, said single-crystal silicon layerhaving a first surface.
 17. The method of claim 16 wherein said at leastone hinge comprises first and second hinge elements, fabricated on saidfirst surface of said single-crystal silicon device layer by a surfacemicromachining technique.
 18. The method of claim 16 wherein said atleast one hinge is created in said single-crystal silicon device layerby a bulk micromachining technique.
 19. The method of claim 17 whereinsaid step d) further includes removing said silicon handle wafer alongwith said insulation layer, thereby revealing a second surface of saidsingle-crystal silicon device layer.
 20. The method of claim 19 whereinsaid step e) includes using a bulk micromachining technique to form saidbulk element in said single-crystal silicon device layer, whereby saidfirst and second surfaces of said single-crystal silicon device layerconstitute said bottom and device surfaces of said bulk element.
 21. Themethod of claim 15 further comprising the step of making said devicesurface optically reflective.
 22. The method of claim 21 wherein saiddevice surface is made optically reflective by depositing a reflectivelayer thereon.
 23. The method of claim 15 wherein said device componentcomprises an epitaxial silicon wafer.
 24. The method of claim 15 whereinsaid support component is fabricated out of an SOI wafer.
 25. The methodof claim 15 wherein said step c) further includes disposing at least oneelectrode in said cavity.
 26. An optical apparatus comprising: aplurality of MEMS devices configured in an array, wherein each MEMSdevice includes: a) a bulk element having a device surface and a bottomsurface, disposed below said device surface; b) a support; and c) atleast one hinge, which is disposed below said bottom surface, and whichis coupled to said bulk element and to said support, thereby suspendingsaid bulk element from said support.
 27. The apparatus of claim 26wherein said bulk element comprises single-crystal silicon.
 28. Theapparatus of claim 26 wherein said at least one hinge comprises firstand second hinge elements.
 29. The apparatus of claim 26 wherein said atleast one hinge is formed from a material selected from the groupconsisting of polysilicon, polyoxide, nitride, silicon nitride, silicondioxide, silicon oxynitride, single-crystal silicon, and metals.
 30. Theapparatus of claim 26 wherein said device surface is opticallyreflective.
 31. The apparatus of claim 26 wherein said support containsa cavity, and wherein said at least one hinge is disposed within saidcavity.
 32. The apparatus of claim 31 wherein said support furthercomprises at least one electrode disposed in said cavity, for causingsaid bulk element to be actuated.